Tailoring Microphase Separation through Backbone Substituent Modulation in Poly(biphenyl alkylene) Anion Exchange Membranes
Junyang Pan, Chenxiao Lin, Tengyu He, Aimei Zhu, Zhaoxiong Xie, Qiugen ZhangAbstract
Anion exchange membrane (AEM) water electrolysis serves as an attractive approach for cost-effective hydrogen generation. However, achieving AEMs with both high ionic conductivity and robust alkaline stability remains challenging. Herein, a series of ether-free quaternized poly(biphenyl alkylene) (PBPN-R) AEMs bearing pendant quaternary ammonium groups with varied backbone substituents are designed and prepared. Among these, the PBPN-CF3Ph membrane, which has a 4-(trifluoromethyl)phenyl backbone substituent, exhibits well-defined microphase separation, resulting in the highest OH– conductivity (141 mS cm–1) and the lowest swelling ratio (18.5%) at 80 °C. Moreover, the PBPN-CF3Ph membrane preserves 88.6% of its original conductivity following a 1440 h aging in 1 M KOH at 80 °C. When implemented in a water electrolyzer, PBPN-CF3Ph delivered a current density of 5.0 A cm–2 at 2.0 V and demonstrated stable operation over 1670 h. This work highlights backbone substituent modulation as an effective strategy for advanced AEMs.